Objectives: The aim of this case-control study was to evaluate the nasopharyngeal pH (NasopH) in children with normal or abnormal pH-metry in two groups of patients; 1) children presenting gastroenterological symptoms; and 2) children with chronic respiratory symptoms.
Methods: From February 2004 to January 2005, all consecutive patients referred for 24-hour pH-metry and in whom gastroesophageal reflux disease was suspected were enrolled in a prospective study. They were assigned to four groups: gastroenterological symptoms with normal (A) or abnormal (B) pH-metries (GG), and chronic respiratory symptoms with normal (C) or abnormal (D) pH-metries (RG). NasopH was measured for 5 minutes, before the 24-hour test was performed.
Results: Thirty-eight pH-metry tests were included (20 in the RG and 18 in the GG). Abnormal pH-metry results were observed in 11 patients in the GG and in 12 in the RG. NasopH means were 6.3273 and 5.6917, respectively (p<0.0001). Average nasopharyngeal pH was 5.6917 among the 12 RG patients with abnormal pH-metry results and 6.5000 among the remaining eight patients with normal test results (p=0.0006). Analysis of the RG with a receiver operating characteristic (ROC) curve showed pH of 5.8 as cutoff point (sensitivity of 91.7% and specificity of 87.5%). The area below the ROC curve was 0.870.
Conclusions: Nasopharyngeal pH is significantly lower among patients in the RG presenting abnormal pH-metry results. A 5.8 NasopH has good sensitivity and specificity and can be used as a screening test in patients with chronic respiratory diseases to select those for whom conventional 24-hour pH-metry is indicated.